1. Field of the Invention
The present invention pertains to a method and apparatus for measuring the attrition rate of particulate material such as used in fluidized bed reactors and catalyzed chemical processes, for example.
2. Background
In certain chemical processes and other manufacturing processes, masses of solid particulate material are physically moved about in such a way that the particles impact each other, or other objects, resulting in breakage and the production of smaller particles or fines. In certain chemical processes such as fluidized bed reactions and catalytic processes, the bed or catalyst material will, over a period of time, suffer an attrition of particles of proper size for continuing the reaction. In certain mechanical processes, quantities of particulate material are used in such a way that the material impacts an object and the particles of the material itself are eventually broken down into finer particles which cannot then be suitably used in the process.
Accordingly, it is desirable to know the attrition rate of various types of particulate material to determine the quality of the material and to plan maintenance operations on a quantity of the material during its use. One particularly important use of large quantities of particulate material is in the catalytic cracking of hydrocarbon fluids to produce hydrocarbons having a lower boiling point than the fluid feed stock. The catalyst material used in such processes must, from time to time, be treated to restore optimum catalytic activity by being passed through a regeneration apparatus or process, which results in mechanical degradation of the material by the formation of smaller particle or fines. The fine material is often of such a size that it cannot be reused in the chemical process and it is desirable to know the rate of attrition which will occur with a quantity of catalyst material so that proper sizing of separation equipment and a schedule of providing makeup quantities of material can be carried out. Moreover, the need to determine the quality of a particular quantity of catalyst material, or other particulate material used in processes which may result in attrition, is clearly desirable so that the material purchased can be rejected or qualified as to its use.
Various types of apparatus are available for measuring the attrition rate of particulate material. An example of a prior art apparatus is disclosed and claimed in my U.S. Pat. No. 4,143,539 which is assigned to the assignee of the present invention. However, the apparatus described in the aforementioned patent is subject to some measurement errors since the fines produced in the test apparatus are not separated from the quantity of material being tested. In this way, the constant commingling of the fines influences the attrition rate and does not give as accurate a determination of average attrition rate as is desired for certain types of measurements. Moreover, the use of such an apparatus does not conveniently provide for the determination of a so-called equilibrium rate of attrition since many samples must be analyzed in the event that one or more samples when analyzed might be samples which are not truly representative of the "hardness" or size of the material being tested.
Accordingly, there has been a continuing need for more accurate determinations of the attrition rate of certain types of particulate material such as fluidized bed reaction materials, catalyst materials used in hydrocarbon conversion processes and materials used in certain types of mechanical treatment processes, for example. In this respect, the present invention is directed to an improved apparatus for determining the average attrition rate of particulate material when subjected to its intended use. The apparatus may be used in an improved method of determining the average or equilibrium attrition rate of a particular type of particulate material.